The present technology is generally directed to treatment of heart disease related to valves of the heart such as percutaneous replacement of the mitral valve. Although specific reference is made to percutaneous replacement of the mitral valve, embodiments of the present technology can provide percutaneous or other treatment of other valves such as the aortic valve.
During a normal cycle of heart contraction (systole), when the left ventricle contracts, the mitral valve acts as a check valve to prevent flow of oxygenated blood back into the left atrium. In this way, the oxygenated blood is pumped into the aorta through the aortic valve. Regurgitation of the mitral valve can significantly decrease the pumping efficiency of the heart, placing the patient at risk of severe, progressive heart failure in at least some instances. The mitral valve regurgitation can be characterized by retrograde flow from the left ventricle of a heart through an incompetent mitral valve into the left atrium.
Mitral valve regurgitation can result from a number of mechanical defects of the mitral valve. The mitral valve includes leaflets and chordae tendineae coupled to the leaflets. One or more of the leaflets, the chordae tendineae, or the papillary muscles may be damaged or otherwise dysfunctional. In at least some instances, the valve annulus may be damaged, dilated, or weakened, thereby limiting the ability of the mitral valve to close adequately against the high pressures of the left ventricle.
The prior methods and apparatuses to treat valves of the heart can be less than ideal in at least some instances. Although open heart surgery can be used to repair valves of the heart, such surgery can be more invasive than would be ideal. For example, suturing opposed valve leaflets together, referred to as the “bow-tie” or “edge-to-edge” technique, can result in improved heart function. However, with open heart surgery the patient's chest is opened, typically via a sternotomy, and the patient placed on cardiopulmonary bypass. The need to open the chest and place the patient on bypass can be traumatic and may have associated morbidity.
Although recent advances in percutaneous technologies have resulted in valve therapies that can be less invasive, such percutaneous therapies can be less than ideal and may have less than ideal outcomes in at least some instances. Although clips may be delivered percutaneously to connect leaflets of the mitral valve to perform an edge-to-edge repair, placement of these clips on the mitral valve can be difficult. For example, the mitral valve leaflets can move and change shape with blood flow and contractions of the heart, such that alignment and placement of a clip on the valve can be more difficult than would be ideal in at least some instances. Further, many patients suffer from mitral valve disease which is not treatable with such clips or other percutaneous therapies so are left with no options other than open surgical repair or replacement.
Percutaneous treatment of the mitral valve can present additional challenges as compared with other valves such as the aortic valve. The methods and apparatus appropriate for the aortic valve may not be well suited for use with the mitral valve in at least some instances. The mitral valve includes clusters of chordae tendineae extending from the valve leaflets to the walls of the ventricle that may interfere with placement of the prosthesis. The shape of the mitral valve, rather than being circular and uniform like the aortic valve, can be an oval or kidney-like shape that may not be well suited for supporting conventional stents of cylindrical configuration. The mitral valve annulus can be distorted and may have an unpredictable and non-uniform geometry, as compared to the aortic valve annulus. Further, whereas the aortic valve annulus is often entirely surrounded by muscular tissue, the mitral valve annulus may be bounded by muscular tissue on the outer wall only. The anterior side of the mitral valve annulus is bounded by a thin vessel wall. The thin vessel wall separates the mitral valve annulus and the left ventricular outflow tract (“LVOT”), which must remain open to allow blood to pass into the aorta. As a result, the stent-type fixation upon which prior transcatheter prostheses rely may not be suitable for the mitral valve because the anterior side of the valve has insufficient radial strength and can distort under the radial force of such a stent, risking occlusion of the left ventricular outflow tract. Moreover, mitral valve disease often is accompanied by (or caused by) gradual enlargement of the native annulus and/or the left ventricle. Thus, treatment approaches which rely upon radial engagement with or outward compression against the native annulus are subject to failure as the size and shape of the annulus changes.
In light of the above, it would be desirable to provide improved treatments for heart valves, such as mitral valve replacement. Ideally, these treatments would decrease at least some of the deficiencies of the prior art, and provide improved percutaneous valve prostheses with greater ease of alignment and improved coupling of the prostheses to tissues of the heart.